In this verse we see how sin continued in the line of Cain. You can see that there was no break in the opposition against God and his will. Lamech was quite openly a violent person who let the survival of the fittest rule this world. That was the way he wanted it. This becomes very clear in these verses.
He was not satisfied with only one wife. He did not remain obedient to the order of marriage as proclaimed in paradise. The Lord made it clear in Genesis 2:24 that marriage is supposed to be a relationship between one woman and one man (see also Matthew 19:4–6). God’s order of creation was callously resisted here.
19 And Lamech took two wives. The name of the one was Adah, and the name of the other Zillah.